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Triticum Agricolam

6th Order Port Area Experiment

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Tuned in. Always love seeing your testing posts. Very informative. 

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After you test the 32hz rear port then bring it down to the mid to high 20's where people realistically tune rear ports for 6th's. 

Smaller rear port is better. Tested it in many different cases myself multiple times. Any data is good data though. :)

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28 minutes ago, Raptorman said:

After you test the 32hz rear port then bring it down to the mid to high 20's where people realistically tune rear ports for 6th's. 

Smaller rear port is better. Tested it in many different cases myself multiple times. Any data is good data though. :)

I can do that.  

I'm glad you commented on what I going to do, I was hoping you would give your input.

Edited by Triticum Agricolam

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I've been chipping away at this project a little bit each day.  I've started my harvest season so I don't have much spare time, but I want to keep working on this experiment as I'm able to. 

I finished construction of the enclosure and two of the port configurations.  I still need to do the lower-tuned port configurations.  I was able to take some impedance measurements of the 6 sq in and 25 sq in port configurations.  Here is the test setup:

5986ad1d45072_2017-08-0322_14_11.jpg.62c198f18f71be67ba8fca1b97f267c1.jpg

 

I took impedance measurements between 20-100 Hz at three different input power levels (2, 21, & 38 volts).  

Here is the results of the large rear port (25 sq in) configuration:

LP.PNG.a9042ccdb24051fceb1a23c52943beb0.PNG

 

Here is the small rear port (6 sq in) configuration:

SP.PNG.3b135848e141cb46dbed610eda3eb466.PNG

 

And here it with the rear port plugged to make it into a 4th order bandpass:

FO.PNG.f68f48299b6dad6b987756cd019f0821.PNG

 

I have a theory as to whats going on with the different port sizes, but I'm going to wait until I get all the testing done before I give my interpretation of the results.  I'm curious to hear what you folks think is going on based on the impedance measurements.

After I get the final two port configurations built and impedance tested I will be doing SPL testing.  To do it right I need to do the SPL testing outdoors.  By the time I set everything up, do the testing, and then put everything away it turns into a several hour project.  I probably won't have time to do that for several weeks, but I'll get it done eventually.  

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Im with 8, sort of.  haha  Im guessing too much port area to play below tuning frequency effectively?  

Maybe the impedance rise caused by a speaker unloading below tuning is more influential to the circuit than impedance rise caused by choking a small port (high velocity=high drag).  They both cause rise, but maybe one is more effective at making rise than the other.  ? :shrug:

But it seems that near the tuning frequency, the large port prevents impedance rise.

Looking forward to more data!  Cool stuff man

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thanks for the update.
Since I am currently building a 6th. I'm really curious to see how this comes out

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